The use of active oxygen sources (e.g. peroxide) with a transition metal catalyst is known to improve bleaching performance; see for example U.S. Pat. No. 5,246,612. The improved efficacy for bleaching is beneficial for removing stains such as tea and/or coffee as well as starch soils on wares. However, the delivery of catalyst materials in detergent formulations, including highly alkaline compositions, suffers from numerous stability challenges. In many instances, formulation of the metal catalysts into solid alkaline detergents suffer from limited stability.
The use of coatings and/or encapsulation of particulate materials has been used for bleaching catalyst granules to increase stability; see for example, GB2428694, WO 03/093405 and WO 02/06659. Similarly, agglomerated forms have been disclosed in EP0072116 and EP0124341, and granules have been disclosed in EP544440, WO 1994021777, WO1995006710 and EP141470. The use of granular detergent products (e.g. formulations for consumer detergent use, see for example U.S. Pat. No. 5,703,034) has been used to incorporate bleach catalysts directly into a granular detergent product; however, stability concerns remain for formulating solid and/or multi-use detergent compositions containing catalysts. Therefore, when formulating solid block compositions there is a need for further stability and segregation of catalysts from the alkaline detergents.
In addition, prior compositions have stabilized catalysts using water soluble ligands or complexing agents, including for example EDTA, DTPA, NTA, and alkaline metal and alkaline earth metal salts, along with alkaline metal tryphosphates and the like, such as disclosed in EP10141470. Such compositions form water and soluble salts with the manganese to attempt to prevent release of magnesium dioxide. Further, use of biopolymers and polysaccharides, including starches is disclosed for use in stabilizing catalysts in U.S. Pat. No. 5,480,575. Sugars, such as mannitol are disclosed in EP2655588 for use with sulfonated polymers as coating materials for catalysts.
However, such methods do not overcome difficulties in use of catalysts, such as storage instability of the catalysts. Moreover, use of commercially-available catalyst materials (e.g. formulations containing metal and protective ligand) requires protection of the metal/ligand catalyst as opposed to prior art's use of water soluble ligands or complexing agents simply stabilizing the metal catalyst itself. A further disadvantage with encapsulates and granules is that they are generally bound to certain particle size constraints. An additional problem associated with such coatings and/or encapsulation is that the materials providing the protection may themselves have an adverse interaction with the component to be protected. Therefore, in some products stability has been increased by removing any easily oxidisable materials from the compositions. However, there remains a need to increase the shelf life of a highly alkaline solid detergent composition containing a catalyst.
The shelf life of a cleaning product may be regarded as the period of time over which the product may be stored while retaining its required performance efficacy. A satisfactory shelf life is in many instances a crucial factor for the success of a commercial product. A product with a short shelf life generally dictates that the product is made in small batches and is rapidly sold to the consumer. Beneficially, products with a longer shelf life may be made in larger batches, maintained in storage for a longer period of time and/or maintained by a consumer for a longer period of time before use. Accordingly, it is an objective of the claimed invention to develop detergents having increased shelf life and stability when employing catalysts.
It is an object of the present invention to mitigate the problems outlined above and/or to further improve the stability of particulate material comprising a bleach catalyst.
A further object of the invention is to provide methods of protection and/or coating a catalyst material in a solid detergent block with a cellulose derivative to protect the catalyst from the alkaline detergent.
Other objects, advantages and features of the present invention will become apparent from the following specification taken in conjunction with the accompanying drawings.